I would recommend quarantining your new chameleon for several months...in a separate room...feeding, cleaning, etc. last and not going back into the room with your other critters. Water it, feed it and leave it alone most of the time so it can adjust to its new home.
I usually let them get accustomed to their new home for a couple of weeks before I take them in for parasite tests/treatment...it can decrease the parasite bloom that often happens under the stress of capture, etc. However, if the chameleon is acting sick, then it will have to be tested/treated sooner.
Just getting a medication for parasites will avoid the cost of the vet, but you won't even know if the chameleon has parasites (some don't) or not and you certainly won't know what the parasites are that it has. So...you won't know if you treated it unnecessarily or got all the parasites or not. You need to know its weight and the strength/dose of the medication you will be giving it too.